Insulated tank cars often include an outer jacket wrapped around an inner hull or shell. An insulating material may be placed between the hull and the outer jacket. The outer jacket serves to protect and contain the insulating material.
Previously, insulated tank car outer jacket fabrication may have included applying strips of steel or other pre-fabricated material directly onto tank car jacket supports or spacers. Each strip may be laid out and carefully placed in order to have symmetrical seams. Following the layout, the seams may be welded and nozzle and bolster openings cut. Care must be exercised during cutting to avoid damaging the insulation applied between the tank shell and outer jacket. Handling may also be critical as lofting and rigging apparatus may crease the outer jacket. Care must also be taken to avoid collapsing or bending the jacket.
Alternatively, insulated tank car outer jacket fabrication may include laying material on a flat surface (such as a floor), arranging the materials according to the required dimensions, welding together some or all of the sections, and then installing the outer jacket on the car shell. Layouts for the nozzles, man ways, and bolsters may be manually applied prior to cutting. After cutting, the sections or completed assemblies may be rigged and lofted into position on the tank shell. This form of jacket fabrication may require enormous floor space and skilled layout personnel. Match lines may also need to be created and aligned so that cutouts match and/or properly align. Layout and fitting may be time consuming and may pose considerable quality control obstacles.
A further alternative insulated tank car outer jacket fabrication method may include the application of Spiral Welding to form a continuous tube. Flat coil material may be fed through a series of rollers that may spiral the strip into a tube. The interfaces of the spiral may be welded as the tube is formed. As the tube progresses, it may be cut to length and moved to an area where additional layout and cutting may be performed. At a separate station, the tube may be cut longitudinally so that it can be installed over the tank. Layouts and cuts for the nozzles, man ways, and bolsters are also made.
Another method of jacket fabrication may include de-coiling several widths of coil stock onto a large diameter mandrel of a jacket jig. The jig may closely match the length and diameter of the tank to which the jacket will be applied. The coil stocks may be wound to a measured length and then oxy-fuel torch cut. This leaves a strip of coil (or sheet of sheet metal) attached to the jig. A second set of coil stock may be wound to the jig after indexing the jig approximately a distance equal to the width of coil. The second set of coil stock may overlap the first set of coil stock by approximately 1″ at the intersections. Tack welds may be applied to the overlap, or lap joints, as the jig is rolled. After tack welding, two to four operators may weld the seam to completion to form the assembly (jacket). Following welding, the jacket may be manually laid out with chalk lines indicating where the cutouts are to be made by oxy-fuel torches at the required locations for nozzles, man ways, bottom outlets, and bolsters. At the completion of cutting, the jacket may be removed from the jig and prepared for installation over the tank car shell.
Prior systems for jacket fabrication have used coil alignment sensors and movable coil support carriages to keep sheets of sheet metal from spiraling onto the mandrel. In instances where it is desirable for the sheets of sheet metal to be wound onto the mandrel without spiraling, alignment sensors may be placed in close proximity to the mandrel. The alignment sensors may be in the form of disks capable of sensing a sheet of sheet metal has become misaligned. The sensors may be coupled for communication with an actuator on the coil support carriage. The actuator may be operable to move the coil support carriage, and thereby the coil, along a track running parallel to the mandrel. The coil support carriage may be moved until the alignment of the sheet of sheet metal being wound onto the mandrel has been corrected. Correct alignment may be determined by the coil alignment sensor, which may indicate to the actuator that the alignment no longer needs adjustment.
Fabricating flat sided jackets usually includes laying out and cutting the area for the flat side from a round jacket. A flat plate may then be welded in place of the cut out section to form a flat on the side of the jacket. The welding and cutting may cause distortion of the sheet metal, leaving waves and creases along the welded surfaces.
Alternatively, a flat side may be formed by passing a width of material through a brake press to crease transverse sections the width of the flat along the length of the coil. The strips may then be wound on a mandrel. As the winding proceeds, the creases transverse of the coil will remain relatively flat. Further work on the flat may be needed to obtain a smooth surface.